The smart antenna technology has become one of the most attractive technologies in the mobile communications, and has been widely used in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system in a 3G mobile communication system.
The key technology of the smart antenna is the beamforming, which changes the directional diagram of an antenna array according to a steering vector of a signal and generates a spatially directional beam, thereby attaining the object of extracting a target signal and suppressing or eliminating interference. Because a smart antenna system performs the signal processing mainly depending on the strong dependency between antenna array elements to realize the beamforming, the space between the antenna array elements is required to be small; at present, the space is set as ½ wavelength in the TD-SCDMA systems. FIG. 11 is a schematic diagram of a smart antenna array in a TD-SCDMA system, where all the array elements of the smart antenna (it is hypothesized that there are N array elements, where N is a positive integer) employ the same polarization mode—vertical polarization, the space between each antenna array element is ½ wavelength, and N antenna array elements act on the beams coming from each direction to carry out the spatial filtering, thus aiming narrow beams with a high gain at the direction of a service user, and aiming null at the direction of the interference, so as to increase the output signal-to-interference ratio of the array, lower the interference in the system, and improve the anti-interference capability of the system.
In an Multiple-Input Multiple-Output (MIMO) or an Multiple-Input Single-Output (MISO), multiple antennas are used to suppress the channel fading or to increase the system capacity, so that multiplexing gain and space diversity gain may be provided to the system, where the spatial multiplexing technology may greatly increase the channel capacity, while the space diversity technology may increase the channel reliability and lower the channel bit error rate, thus it is regarded as the key technology of the physical layer in the systems such as a Long Term Evolution (LTE) and a WiMax. Because an MIMO/MISO system obtains the diversity gain mainly by using the independence of the space channel fading features of the different antennas, the space between the antenna array elements is required to be large, and theoretically, the space between the antenna array elements is required to be about 10 wavelengths.
Because different requirements are laid on the antenna dependency in a smart antenna system and an MIMO/MISO system, the large-scale reconstruction and modification of the antenna system may be faced during the future system evolution process. To solve this problem, and to integrate the smart antenna system and the MIMO/MISO system, in the prior art, either all of the antenna array elements in the original smart antenna system are simply divided into two groups, or the remote end antenna array elements are selected as the transmitting antennas in the specific situations.
In the solution of simply dividing all of the antenna array elements in the original smart antenna system into two groups, only a two-antenna system in a broad sense is formed from the original antenna array elements, but there still exists a very strong dependency between these two broad-sense antennas, and the corresponding diversity gain cannot be obtained. Moreover, in the solution of only selecting the remote end antenna array elements as the transmitting antennas, a different power amplifier from that of the original smart antenna system needs to be employed (since in order to guarantee the comparability, the sum of the powers of the two remote end antenna array elements is equal to the sum of the powers of all the antenna array elements in the original smart antenna system); and in such a solution, when the remote end antenna array elements are taken as the multiple input antennas of the MIMO/MISO system, the two remote end antenna array elements till have strong dependency theoretically, and cannot be further used for beamforming at the same time.
When a part of the antenna array elements (the remote end antenna array elements) in a smart antenna system is used for an MIMO/MISO system, other antenna array elements (the intermediate antenna array elements) should be set in off state; otherwise, all the antenna array elements will work according to the original smart antenna system. This relates to the allocation of the antennas and the public channel resources among different systems, thus causing the decrease of the system efficiency, thereby causing the decrease of the system throughput.